IF he cares about your feelings, he needs to stop. My boyfriend and I are very comfortable in talking about what we find attractive in someone else but we know when to draw the line. Beside your boyfriend should be saying, "The one person I want to do the most is you." If he loves you enough he shouldnt be constantly thinking about other women...if this issue persists you might really need to think about why exactly you're still with him and if this issue is going to hinder moving forward in your relationship with him. You have every right to feel what you are feeling and he should respect it. If not then I think that is a red flag.